This application is one of a pair of applications that seek funding to continue the national study, Monitoring the Future (MTF). It seeks a five-year continuation of data collection in the cohort-sequential panel studies. The investigators will continue to measure and study changes in substance use and related factors across historical periods and across the life course (up to age 50), using multiple samples of high school graduates first surveyed in 12th grade by MTF. The proposed continuation will extend these very rare, nationally representative panels that now cover up to 30 years of the life span. Highly cost-efficient mailed surveys will continue to be conducted biennially to age 30, and once every five years thereafter, to age 50. Individual and social contextual factors, including role and social context transitions that may explain change and stability in drug use, will be measured. The research objectives are: (i) to continue to track historical change in substance use by important segments of the general adult population, including college students and other young adults, as well as those in middle age;(2) to document the natural history of drug use and related attitudes from adolescence into middle adulthood, including later substance use disorders (abuse and dependence);(3) to extend the age band covered to age 50;(4) to continue to study and track risk and protective behaviors associated with the spread of HIV;(5) to distinguish among three different types of change taking place-period, age, and cohort;and, (6) to study the causes, consequences, and developmental patterns associated with each type of change. (The three types of change have different determinants and timing of action and MTF has demonstrated that all three have occurred for most drugs.) Factors that may explain historical trends and cohort differences will also be monitored. Other hypothesized psychological, behavioral, and social determinants of drug use (including attitudes and beliefs, peer norms, and availability) will be measured, as well as a range of potential consequences of drug use (including physical health, drug abuse and dependence, psychological well-being, status attainment, and role performance). The investigators will continue to facilitate use of MTF data by others. Study results should have major implications for understanding (and preventing) drug use and abuse, and the spread of HIV.